It is known that chlorine is useful as a raw material of vinyl chloride, phosgene, etc., and can be produced by oxidation of hydrogen chloride. In Japanese Patent Kokai (Laid-Open) No. 62-270405, for example, a process for producing chlorine comprising oxidation of hydrogen chloride using a chromium oxide catalyst is described. However, the process which has hitherto been known has the problem that the catalyst activity is insufficient, and it has been desired to develop a catalyst having high activity, which can be used for the oxidation reaction of hydrogen chloride.
When using a supported ruthenium catalyst for a general oxidation reaction with oxygen, ruthenium in the high oxidation state was sometimes volatilized at an elevated temperature. Therefore, it has hitherto been considered difficult to use the supported ruthenium catalyst for that reaction. The present inventors have found first that the ruthenium catalyst shows high activity when using it for the reaction for producing chlorine by oxidation of hydrogen chloride, and have studied more intensively. Thus the present invention has been completed.